Mb. Thomas et Ne. Jenkins, EFFECTS OF TEMPERATURE ON GROWTH OF METARHIZIUM FLAVOVIRIDE AND VIRULENCE TO THE VARIEGATED GRASSHOPPER, ZONOCERUS-VARIEGATUS, Mycological research, 101, 1997, pp. 1469-1474
The temperature optima for germination, radial hyphal extension rate a
nd sporulation were determined for two isolates of Metarhizium flavovi
ride from acridoid hosts. 191-609 exhibited lower temperature optima f
or hyphal extension (25.5 degrees C) and sporulation (24 degrees) than
IMI 330189 (27 degrees and 25 degrees, respectively), although temper
ature optima for germination were similar (ca 30 degrees). The tempera
ture optimum for sporulation was lower than that for hyphal extension.
Further studies were carried out on 191-609 to investigate the effect
of temperature and dose on the infection mortality rate of the grassh
opper pest, Zonocerus variegalus. Increasing dose resulted in a decrea
se in mean survival time regardless of incubation temperature. Dose an
d temperature were shown to interact, with the effects of dose increas
ing at temperatures either side of the optimum. Furthermore, for each
dose, the optimum temperature for infection was estimated to be ca 5 d
egrees higher than the optimum for growth, and no significant relation
ship was identified between hyphal extension rate in vitro and host su
rvival time. The implications of these results are discussed with rega
rd to the selection of isolates for use in biological control.